1. Field of the Invention
The present invention relates to the stabilization of organic substrate materials to exposure to light and particularly, to the stabilization of organic dyestuffs for exposure to light. More particularly, the present invention relates to stabilizing organic substrate materials in the form of photographic dye images and to novel photographic elements so stabilized.
2. Discussion of the Prior Art
The tendency for organic substrate materials; for example, organic dyestuffs, to fade or to discolor when they are acted on by light has been widely known, and various studies for preventing such fading or discoloring phenomena of organic dyestuffs from occurring, that is, for improving light fastness thereof have been attempted in the arts of preparation of ink, textile dyeing, color photography and the like. The present invention is applicable to a great advantage in improving light fastness of organic substrate materials.
In the present specification, the terms "organic substrate material" and "substrate material" include substances which are colored or colorless to the human eye under exposure to sun light, including not only substances having absorption maximum in the visible region but also substances having absorption maximum in the near ultraviolet region; for example, optical whitening agents and substances having absorption maximum in the infrared region. In the present invention, organic substrate materials include organic substances having absorption maxima in the wavelength region of about 300 nm (in the ultraviolet region) to about 800 nm (in the infrared region). These organic substrate materials occur particularly in photographic materials, e.g., color films, prints, diffusion transfer units, etc., in colored polymers useful as agricultural vinyl cover sheets, umbrellas, tents, etc.; fluorescent whitening agents; and dyed textiles, etc., and this invention is directed to improving the light fastness of these materials in each of these environments.
The term "dye" or "dyestuff" in the present specification includes organic substances which appear to be colored to the human eye under exposure to sun light.
The term "light" in the present specification means electromagnetic waves of a wavelength less than about 800 nm, including ultraviolet rays less than about 400 nm, visible radiation of about 400 nm to about 700 nm, and infrared rays of about 700 nm to about 800 nm.
Hitherto, it has been known that organic substrate materials such as dyes or dyestuffs tend to fade or to discolor when exposed to light, and a number of reports relating to methods of preventing such a fading or a discoloring phenomena, that is, methods of improving the light fastness of the organic substrate materials have been proposed. For instance, the improvement of the light fastness of organic compounds, such as indophenol, indoaniline, azo and azomethine dyes, to visible and ultraviolet lights by mixing with fused heterocyclic ring-containing phenol type compounds, is disclosed in U.S. Pat. No. 3,432,300.
In the art of silver halide photographic light sensitive materials, azomethine or indoaniline dyestuffs are generally produced by the reaction of an oxidized aromatic primary amine developing agents with color couplers, as described in C. E. K. Mees & T. H. James, The Theory of the Photographic Process, Chapter 17, Macmillan, New York (1967). A great number of compounds used for improving the stability of color images made up of these dyestuffs to light are known. For example, hydroquinone derivatives are disclosed in U.S. Pat. Nos. 2,360,290; 2,418,613; 2,675,314; 2,701,197; 2,704,713; 2,728,659; 2,732,300; 2,735,765; 2,710,801 and 2,816,028; and U.K. Patent No. 1,363,921: gallic acid derivatives are disclosed in U.S. Pat. Nos. 3,457,079 and 3,069,262; Published Japanese Patent Publication No. 13,496/68; and so on: p-alkoxyphenols as disclosed in U.S. Pat. Nos. 2,735,765 and 3,698,909: chroman and coumaran derivatives as disclosed in U.S. Pat. Nos. 3,432,300; 3,573,050; 3,574,627; 3,764,337; 3,574,626; 3,698,909 and 4,015,990: and so on are known. However, these compounds alone are insufficient to effectively prevent color images from fading or discoloring.
Still another method of improving the stability of organic substrate materials to light wherein azomethine quenching compounds having their absorption maximum at a corresponding longer wavelength resion than that of the absorption maximum of the substrate material are employed is described in U.K. Pat. No. 1,451,000. However, this technique suffers the disadvantage that because the azomethine quenching compounds themselves are colored intensely, they exert a serious influence upon the hue of the substrate materials.
Furthermore, the use of certain metal complexes with the intention of preventing colored polymers from deteriorating by exposure to light is reported by J. P. Guillory & R. S. Becker, J. Polym. Sci., Polym. Chem. Ed., volume 12, page 993 (1974) and R. P. R. Ranaweera & G. Scott, J. Polym. Sci., Polym. Lett. Ed., volume 13, page 71 (1975). Similarly, a method of stabilizing dyestuffs using metal complexes is disclosed in Published Japanese Patent Application (OPI) No. 87,649/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) and Research Disclosure 15162 (1976). However, the deterioration-inhibiting effect of such metal complexes is not so powerful and the solubility of such metal complexes in organic solvents is relatively low so that they cannot be added in an amount high enough to exert a sufficient antifading effect. In addition, these complexes are intensely colored in themselves. Therefore, the addition of a large amount of these metal complexes has the disadvantage of adversely affecting the hue and the purity of the organic substrate material and particularly, dyestuffs.
Furthermore, agents suitable for preventing fading and discoloration of cyan dyes and cyan dye images have not been known.